I like to use Clenzoil, I only use it on the outside of the gun. When on a hunt or out shooting, I like to carry a soft flannel rag coated in Clenzoil (keep it in ziplock) to wipe down barrels and trigger guard before putting the gun away.

A gunmaker friend of mine likes to use this oil and grease to lube the guns guts when he does strip and cleans for clients. http://nyelubricants.com/
I have started using this lubricant as well for internal parts/mechanisms.

The gentleman who got me into doubleguns always used Singer Sewing Machine oil to lube the guts when he stripped and cleaned his guns.

I believe Rocketman likes to use this stuff..http://www.mousemilk.com/

Dustin